1. Field of the Invention
The present invention relates to a camera module for an endoscope and an endoscope.
2. Description of the Related Art
For example, an endoscope includes an insert unit that is inserted into the body of a patient. The insert unit includes a distal end hard portion, a curved portion, and a soft portion in this order from the tip. Moreover, an observation window, an illumination window, a forceps outlet, and an air and water supply nozzle are provided in the tip surface of the distal end hard portion. In addition, in the inner surface of the distal end hard portion, a camera module is mounted at a position corresponding to the observation window and a light guide is mounted at a position corresponding to the illumination window respectively. The curved portion is configured so as to connect a plurality of joint ring units and cause the distal end hard portion to be directed toward a desired direction through a wire operation. The soft portion has a length of about 1 m to 2 m for making the distal end hard portion reach a desired observation portion of a subject.
The camera module includes a photographic lens unit and an imaging unit. The photographic lens unit is configured to accommodate a plurality of lenses in the housing. The imaging unit includes an image area sensor such as a CCD or a CMOS that converts an optical image imaged by the photographic lens unit to image signals. The image area sensor is connected to a transmission cable via a circuit substrate such as a flexible substrate or a sub-board. In addition, electronic components for driving the image area sensor are mounted to the flexible substrate or the sub-board. Signals from the imaging unit are sent to an image processor via the flexible substrate or the sub-board and the transmission cable. The image processor performs image processing of the signals and displays images such as a lesion on a monitor.
The transmission cable that sends the signals from the imaging unit to the image processor is configured of a compound multicore cable. Since the transmission cable is inserted over the entire length of the insert unit, the transmission cable is strongly pushed and pulled whenever the insert unit is looped or curved. If the transmission cable is pulled into the insert unit, junctions of the substrate may be separated or the transmission cable may be cut.
In order to avoid the separation or the cutting, various suggestions have been made. For example, in an endoscope disclosed in JP1993-261064A (JP-H05-261064A), a transmission cable is soldered to one end side of a flexible substrate, the flexible substrate is bent in a U form so as to surround the soldered transmission cable, the periphery of the bent flexible substrate is covered using a shield tape and an insulating tape, and epoxy-based adhesive is filled into the inner space of the tapes and is hardened so as not to be deformed. In addition, since the circuit substrate of the side in which the transmission cable is fixed is fixed to a connection tube through a fixing screw via a pressing plate, even when the transmission cable is strongly pushed and pulled, the circuit substrate does not move, and torsion or an inclining force that is applied to the circuit substrate from the transmission cable is absorbed by the circuit substrate having flexibility and is not transmitted to the image area sensor and an object optical system.
In a camera module disclosed in JP1997-146011A (JP-H09-146011A), a sealing material covers a connection unit between a flexible substrate and a transmission cable and is hardened.
In a camera module disclosed in JP2008-118568A, a reinforced frame that accommodates an image area sensor and an electronic component mounting unit of a flexible substrate is provided, and an adhesive material is filled into the inner side of the reinforced frame. In addition, the tip portion of a transmission cable that is soldered to the flexible substrate and the reinforced frame are covered using a heat shrinkable tube, and an adhesive material is filled into the inside of the tube and is sealed.
In a camera module disclosed in JP2004-283486A, a mechanism that changes a focal distance of a photographic lens is provided, and the focal distance can be switched between a general observation and an enlargement observation. In such a camera module, a photographic lens unit and an imaging unit lens are configured so as to be separated and are fixed to the photographic lens unit via a prism holder of the imaging unit and integrated with each other, and the camera module is thus configured.